It is well known that vehicles have come in recent years to be provided with one or a plurality of inflatable airbags, with a view to protecting occupants, and in some cases also pedestrians, during a vehicle accident. Airbags are ordinarily formed of a flexible fabric, but some other flexible sheet material, such as plastic materials, are used in some cases. Airbags come in various forms, for instance so-called driver airbags that protect the driver by inflating from the vicinity of the center of the steering wheel of an automobile, curtain airbags that protect an occupant during a side impact, or during a rollover or overturn accident, by deploying downward on the inward side of an automobile window, and also side airbags that deploy between an occupant and a side panel of the vehicle interior, so as to protect the occupant during a side impact. The present invention is optimal mainly for curtain airbags, but can also be used in airbags of other types without any particular limitations.
The useable space available for accommodating airbag devices is ordinarily limited, and is often designed to be very small. There are various conceivable reasons for this, for instance aesthetic considerations, and considerations pertaining to the comfort and convenience of the occupants. Accordingly, airbags that are packaged by compression and that take up only a small space in a rolled and/or folded-up state when not deployed are well known.
For instance, structures have been proposed that are provided with a hard plastic cover around an airbag, in order to maintain the packaged state of the compressed airbag and to facilitate attaching of a unit to an automobile, in a simple and reliable manner. However, this significantly increases the cost and weight of an airbag unit, and also the volume of the packaged airbag, and accordingly it is difficult to produce an airbag unit of sufficiently small size. Moreover, a large space is also required during transport, which translates into higher transport costs, due to the fact that the airbag is covered by the hard cover.
Elongately compressed curtain airbags are prone to twisting, and are difficult to position with respect to vehicle attaching portions. Moreover, it has been difficult to grasp the twisted state that arises also when the airbag twists during attaching to the vehicle. The deployment behavior of the airbag during operation could be affected were the airbag hypothetically attached in a twisted state.